The limbic system

Neuronal circuitry controls of emotional behavior and motivational drives

Composed of subcortical and cortical components

Limbic System
Figure 12.18

limbic

Hypothalamus ,septum,paraolfactory area,epithalamus,ant.thalamic nuclei,hippocampus,amygdala,basal gangeli

Limbic cortex

Orbitofrontal coretx,subcallosal gyrous cingulate gyrus and parahippocamp gyrous

Limbic System: Emotion and
Cognition

The limbic system interacts with the prefrontal lobes, therefore:

One can react emotionally to conscious understandings

One is consciously aware of emotion in one’s life

Hippocampal structures – convert new information into long-term memories

The hypothalamus not only influences how you feel, it influences how you interpret the consequences of those feelings.

limbic

Visceral
Afferents
Hypothalamic Role in Emotion
Hypothalamic
Nuclei
Hormonal
Output
Nucleus of the
Solitary Tract
Autonomic
Output
Brain Stem
Nuclei
Autonomic
Preganglionic
Nuclei
Target
Organs

Hypothalamus
Pituitary
Releasing Factors
Autonomic
Nervous System
Adenohypophysis
(Anterior Pituitary)
Neurohypophysis
(Posterior Pituitary)
Sympathetic
Parasympathetic

stria terminalis
Amygdala
Cortex, septum medial forebrain bundle
Hypothalamus mtt
Anterior Nucleus dorsal long.
Brainstem fasciculus
Amygdala ventral route ant.
parvo magno
(SO, PV) medial forebrain bundle post.
Brainstem spinal cord
Pituitary

Hypothalamus,Major

Hypothalamus is the most important output sorce

It communicate with brain stem by medial forebrain bundle ,bidirectionaly between forebrain and brain stem

Hypothalamus cont.

Controls:
1-vegetative and endocrine functions
2-behavior and motivation

vegetative and endocrine functions

Cardiovascular regulation involves
1-Post. And lateral hypothalamus area, increase
BP and HR.
2-preoptic area ,decrease BP and HR
*1and 2 mediated by cardiovascular centre in the pontile and medullary part of reticular formation

Body temperature regulation

Preoptic area

Thermo-regulation
(body temperature)

Involves autonomic nervous, endocrine, and skeletomotor systems

Body temperature detectors

Peripheral: skin, spinal cord, viscera

Central: anterior hypothalamus

Body temperature effectors

Heat retention or generation: posterior hypothalamus

Heat dissipation: anterior hypothalamus

Thermo-regulation
(body temperature)

Heat dissipating mechanisms

Dilation of blood vessels in the skin

Inhibition of shivering

Heat conserving mechanisms

Vasoconstriction of blood vessels in the skin

Shivering

Increased secretion of thyroxin

Response to Cold Response to Heat
Methods of thermo-regulation by the body

Regulation of body water intake

Thirst centre,lateral hypothalamus

Electrolyte concentrationmaking desire to drink

Supraopticx:urinary excrition due to ADH

Thirst

Function of serum osmolality and blood volume

Osmotic receptors in the hypothalamus

Volume receptors in the right atrium of the heart and great veins

Vasopressin release from hypothalamus

Increases water reabsorption from the kidney

Inhibited by ethanol

Circadian Rhythm

Oscillations during the course of the day

Corticosteriods

Feeding and drinking behavior

Growth hormone secretion

Lesions of the suprachiasmatic nuclei of the hypothalamus disrupts these oscillations


Feeding
Complex interaction of many systems

Regulation of energy metabolism by the
Ventromedial and Lateral nuclei of the hypothalamus

Physical Lesions produce hyperphagia and obesity or reduced attention to food.

Amygdala may also be involved indirectly

Lesions produce hyperphagia-like symptoms

Ventromedial hypothalamic lesions also cause increased insulin secretion Obesity.

Feedback Mechanisms Controlling
Feeding

Feedback from gut hormones
 e.g. Cholecystokinin

Released from small intestine in response to feeding

Inhibits or suppresses feeding

Uterine contraction and milk ejection

Oxytocin stimulation by PARAVENTRICULAR

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Hippocampus circuit

Ent. cortex From perforant To dentate gyrous mossy fiber cA3 schaffer collaterals cA1 to subiculum to ento cortex